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Packet Sniffing with Winpcap Functions Ported to a .NET Library

, 25 Mar 2009 GPL3
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Using Winpcap functions in the .NET Framework
Sample Image - dotnetwinpcap.jpg


Winpcap has been the de facto library in packet capture applications, but the problem is that it is only natively available for C++ and C.

This is an attempt to port some of the crucial Winpcap functions for the .NET environment. The demonstration project here is written in C#.

First of all, you need to install Winpcap from winpcap's Web site and then extract the project zip file. Be sure to reference dotnetwinpcap.dll in the project if not already so.

Methods Available

  • static ArrayList FindAllDevs()

    Returns an ArrayList of Device objects, each describing an Ethernet interface on the system.

  • bool Open(string source, int snaplen, int flags, int read_timeout)

    Opens an Ethernet interface with source as the name of the interface obtained from a Device object, snaplen is the max number of bytes to be captured from each packet, flags=1 means promiscuous mode, read_timeout is the blocking time of ReadNext before it returns.

  • PCAP_NEXT_EX_STATE ReadNext( out PacketHeader p, out byte[] packet_data)

    Reads a next packet and return the packet details (size and timestamp) to object p, and packet raw data in packet_data (array of bytes).

  • void StopDump()

    Stops dumping of capture data to a file.

  • bool StartDump(string filename) 

    Starts dumping of capture data to a file.

  • bool SetMinToCopy(int size)

    Sets the minimum number of bytes required to be received by the driver before OnReceivePacket fires. Lowering this can increase response time, but increases system calls which lowers program efficiency.

  • bool SetKernelBuffer(int bytes)

    Sets the number of bytes in the driver kernel buffer for packet capture. Increase this to avoid packet loss and improve performance. Default is 1 MB.

  • void StartListen()

    Starts listening for packets.

  • void StopListen()

    Stops listening for packets.

  • void Close()

    Stops all operations and releases all resources.

  • bool SendPacket(byte[] rawdata)

    Sends bytes contained in rawdata over the wire. The ethernet checksum will be automatically added prior to sending the packet. Returns true if send is successful, false otherwise.


  • bool IsListening

    true if the dotnetWinpcap object is listening, false otherwise.

  • string LastError

    Returns the last error encountered by the library, if any.

Event Support

delegate void ReceivePacket (object sender, PacketHeader p, byte[] s);
event ReceivePacket OnReceivePacket;

Once StartListen() is called, OnReceivePacket will start to fire on every packet encountered, until StopListen() is called, or Close() is called.

Delegate objects of the above signature may be attached to the OnReceivePacket event to receive notification and perform further processing, as demonstrated in the demo source code.


  • 28th May, 2003: Initial post
  • 25th Aug 2003 - Updated source code
  • 28th June, 2008: Updated source code
  • 24th March, 2009: Updated source code to include client code as requested by Ashin


This article, along with any associated source code and files, is licensed under The GNU General Public License (GPLv3)


About the Author

Victor Tan

Australia Australia
No Biography provided

Comments and Discussions

QuestionHow the source code works in visualstudio2012 PinmemberMember 1123070212-Feb-15 20:31 
GeneralMy vote of 5 PinmemberMiklo B27-Oct-14 12:44 
QuestionNeed help to Show the Dump in RichTextBox instead of File PinmemberMiklo B27-Oct-14 12:43 
QuestionAdding packet filtering [modified] PinmemberChris00319-Jun-12 9:22 
QuestionAccessViolationException PinmemberMember 864901414-Jun-12 1:48 
GeneralCross threading PinmemberOj500025-May-11 5:48 
Generalhelp to convert to C++/CLI Pinmembermiki itz clutch18-Feb-11 2:54 
GeneralPcap.Net - a full WinPcap .NET wrapper Pinmemberbrickner26-Feb-10 7:17 
GeneralThanks!! Pinmemberyuriyag4-Feb-11 0:00 
GeneralWinCe PinmemberMPH195621-Feb-10 1:12 
GeneralWinCE PinmemberMPH195621-Feb-10 1:10 
GeneralC# Sample-Project dont works with c# 2008 Pinmembereightbitwitch4-Feb-10 13:41 
GeneralRe: C# Sample-Project dont works with c# 2008 PinmemberMember 643011-May-10 6:09 
AnswerRe: C# Sample-Project dont works with c# 2008 Pinmemberboblogan9-Sep-10 5:11 
GeneralGet all Packet, inclusive Packets with Set FIN-Flag Pinmembereightbitwitch4-Feb-10 8:17 
GeneralSendPacket are not public - Not acces from VB9 Pinmembereightbitwitch4-Feb-10 8:11 
GeneralChanges required to run on Vista 64 in Visual Studio 2008 PinmemberUmopepisdn5-Jan-10 0:43 
Generalthanks Pinmember791671158-Sep-09 23:28 
General??? please help PinmemberJordan Wis15-Aug-09 17:28 
GeneralMy vote of 1 Pinmemberlegion_9-Jul-09 11:44 
Generalcraft packet PinmemberUnruled Boy1-Jan-09 16:37 
GeneralFull source uploaded PinmemberVictor Tan28-Jun-08 8:25 
GeneralRe: Full source uploaded PinmemberAnil Maurya24-Oct-08 4:45 
GeneralRe: Full source uploaded PinmemberVictor Tan24-Oct-08 5:30 
QuestionDecoding packets PinmemberTariqHussain2-Jan-08 0:13 
QuestionIs it possible to develop a packet sniffer with out WinPcap? PinmemberDiana Fernandez13-Nov-07 0:30 
AnswerRe: Is it possible to develop a packet sniffer with out WinPcap? Pinmemberwurzel_cidermaker28-Jun-08 7:58 
Questionexample for VB.NET 2005 ? Pinmembertecnicosht19-Jun-07 6:03 
Questionupgrade to .net 2005 ? Pinmemberranchu panchu11-Jun-07 10:50 
AnswerRe: upgrade to .net 2005 ? Pinmemberranchu panchu17-Jun-07 20:13 
GeneralRe: upgrade to .net 2005 ? Pinmembercooke12313-Nov-07 21:36 
QuestionUrgent:winpcap with realbasic? Pinmemberinfantilo28-Nov-06 10:10 
Questionget the content? Pinmemberdennis02061-Nov-06 3:33 
AnswerRe: get the content? Pinmemberdennis02061-Nov-06 4:51 
Generalread a file.acp PinmemberDanieleBianchi21-Sep-06 6:55 
QuestionHow to get the payload of packet PinmemberAmol pathak17-Sep-06 21:16 
QuestionI need codes in JAVA in order to read, save and use Packets captured from VoIP traffic?? (UDP) Pinmemberandre_toro9-Aug-06 10:28 
Questiondotnetwinpcap.dll ??? Pinmemberpgr_home2-Aug-06 10:08 
GeneralNo packet data! PinmemberLady-green27-May-06 22:52 
GeneralRe: No packet data! Pinmemberspeedofspin19-Jul-06 6:31 
GeneralMore detail on needed changes in order to capture all of the traffic Pinmembermobiledeveloper57-Jan-10 17:10 
GeneralDo Not Decompile Pinmemberpunkbuster9-Feb-06 7:06 
GeneralAssembling packets Pinmembervetris11131-Jan-06 22:16 
GeneralUpdated Version PinmemberShawn M Lewis24-Nov-05 16:12 
GeneralRe: Updated Version Pinmemberdjaxl24-Jan-06 11:16 
GeneralMail me the source code pls Pinmembernunomag28-Oct-05 21:07 
GeneralRe: Mail me the source code pls PinmemberHamid Qureshi30-Oct-05 17:59 
GeneralRe: Mail me the source code pls Pinmemberdjaxl24-Jan-06 11:14 
GeneralRe: Mail me the source code pls Pinmembernunomag25-Jan-06 0:35 
GeneralRe: Mail me the source code pls Pinmemberpunkbuster6-Feb-06 12:55 

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